Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $92.81   4.326%   $96.825   $96.83   $96.85   $96.80  
  Purchase #2 $158.28   11.617%   $176.6674   $176.67   $176.65   $176.70  
  Purchase #3 $149.90   4.259%   $156.2842   $156.28   $156.30   $156.30  
  Purchase #4 $86.46   10.113%   $95.2037   $95.20   $95.20   $95.20  
  Purchase #5 $23.73   3.117%   $24.4697   $24.47   $24.45   $24.50  
  Purchase #6 $179.39   10.833%   $198.8233   $198.82   $198.80   $198.80  
  Purchase #7 $226.62   4.464%   $236.7363   $236.74   $236.75   $236.70  
  7 purchase totals = $917.19       $985.0096   $985.01   $985.00   $985.00